I'm using CopyQ (and SyncThing) right now. Its design limits the number of entries, and sync doesn't work very well.
Nobody needs yet another clipboard manager as there is almost a perfect one out there. Which can be extended by plugins! (I don't think it's a valid approach to start a new project because some project doing most of the wanted stuff isn't "perfect". The result is almost always "yet another 80% solution").
The "limited" number of entries is not an issue, imho. You can set it to x-thousand entries if you like. (One thousand entries are enough for more than two weeks of history for me. A clipboard is not a means of permanent data storage at all so this is fine; even one can have something akin to permanent entries by just using tabs in CopyQ).
Implementing in CopyQ some of the suggestions mentioned here would be great though!
You can read the issue I filed in CopyQ's repository back when I switched to Linux and had to stop using Ditto for the justifications of infinite history: https://github.com/hluk/CopyQ/issues/510
CopyQ is also bound to use Qt's clipboard implementation, which provides the common subset of Qt's supported platforms, with all the consequent limitations. See the other issues I filed for details.